Method of making molds for continuous casting machines

ABSTRACT

A method of making molds for use in continuous casting machines is disclosed, wherein a mandrel is forced into a pipe for the latter to assume overall configuration of the mandrel. The pipe is cold-worked on the mandrel to assume contour thereof in detail of surface configuration, the pipe is removed therefrom subsequently.

United States Patent [151 3,646,799 Kipp et al. 1 Mar. 7, 1972 [5 METHOD OF MAKING MOLDS FOR e ces Cited CONTINUOUS CASTING MACHINES UNITED STATES PATENTS [72] Inventors: Adolf Kipp; Heinz Payk, both of 252,423 1/1882 Buckingham ..72/283 Osnabruck, Germany 1,378,639 5/1921 Warner ..72/370 1,881,121 10/1932 Ford et al. .....72/370 Assleneer Rebel-11nd Melllwem Gutchofl- 2,392,797 1/1946 Hackett ..72/37o nunashum Akhensesellschnfl, Hannover. 2,938,263 5/1960 Kruger ..72/37o Germany Primary Examiner-Lowell A. Larson [22] filed 1969 Attorney-Smyth, Roston & Pavitt [2i] Appl. No.: 885,126

ABSTRACT 52 US. Cl. ..72/370,164/6, 164/273 Amelhod of making molds for use in continuous casting 5 hm an 51/00 machines is disclosed, wherein a mandrel is forced into a pipe [58] Field Search 264 164/6 82 for the latter to assume overall configuration of the mandrel. The pipe is cold-worked on the mandrel to assume contour thereof in detail of surface configuration, the pipe is removed therefrom subsequently.

5 Claims, 2 Drawing Figures METHOD OF MAKING MOLDS FOR CONTINUOUS CASTING MACHINES The present invention relates to a method for making a mold for a machine for continuous casting, the mold to be made particularly as a metallic pipe. For continuous casting of high-melting metals, such as iron and steel, it is conventional to use molds which are either a single part or multipart. A single-part mold is comprised of a hollow elongated element with a prismlike or cylindrical cross section. Such a tubular mold is made, for example, of pure copper as such a material has high thermal conductivity is one'one of the reasons of its employment. Heavy-duty molds particularly for continuous casting of small or medium size ingots have been made some times of copper with particular additives causing particular hardening while maintaining the high conductivity.

For the manufacturing of curved copper pipe molds, for example, of circle-arc-type machines, it was customary to proceed as follows. First, a particular straight pipe was filled with different types of more or less loose fillings and subsequently the filled pipe was bent to assume the desired configuration. However, this mode of obtaining a curved pipe led to upsetting of the inner and stretching of the outer wall portion of the pipe in the bend and with reference to the resulting are or curve, so that the cross section of the pipe changed, and as result the well-known trapezoidal contour was obtained for the mold. Furthermore, this particular mode of manufacturing curved pipes for a continuous casting machine did not permit maintaining of the desired tolerances of the pipe, in cross section as well as in the longitudinal direction. For example, the desired longitudinal tolerance is below i 1 mm. for a pipe length of 700 to 800 mm., but this tolerance limit could not be maintained when proceeding in that manner. Moreover, another disadvantage of this method is to be seen in that the pipe must have a relatively low hardness to permit bending. On the other hand, the final mold requires considerable hardness, namely up to 70-90 kilograms (weight) per square millimeter (about 50 to 64 tons per square inches).

It isan object of the present invention to obviate the disadvantages and difficulties arising from the manufacturing of molds to be used for continuous casting when reshaping metal pipes; it is a particular object of the invention to provide a new method for obtaining a curved pipe to be used as mold in a continuous casting process. In accordance with the present invention, a straight pipe is provided. Such a pipe can be made in any suitable manner, it can be cast, pressed, drawn or made by any of the known methods of making pipes. The basic implement for forming the mold is a mandrel which has an outer contour representing the desired inner contour for the mold to be made. In particular the mandrel has cross section representing dimension and shape of the desired mold. Furthermore, the mandrel may already have the desired curved configuration if a curved mold isto be made, but the invention principle permits selection of other shapes for the mandrel and for the mold about to be made. This mandrel is forced into the pipe so that the latter is forced to assume the overall contour of the mandrel. Subsequently the pipe is cold formed and worked, so that the inner surface of the pipe assumes the contour of the outer surface of the mandrel in detail of surface configuration and contour. Finally, the mandrel is removed from the pipe.

As aresultof the cold-working, the strength of the pipe has been increased. This pipe, now about to serve as a mold for continuous casting, has dimensions which are accurate within very low tolerances. The pipe has high surface quality and a hardness which is sufficient for utilization as a mold. These properties for the manufactured curved-mold pipe can be obtained in accordance with the method of the present invention independently from the point whether the mold is to be a curved one or whether it remains straight with or without flanges, whether the mold is straight or curved with constant inner cross section or with a conical inner contour. It is important that the quality of the mold made inthis manner is very high, regardless whether it is straight or curved and has rectangular, square-shaped, polygonal or cylindrical cross section.

In order to practice the present invention the outer dimensions of mandrel, be it curved or a straight one, should be selected just a trifle smaller than the inner diameter of the pipe to be used; this requires the mandrel to be forced into the pipe. In general, the first step for shaping this pipe causes the pipe to assume an overall configuration as forced upon it by the contour of the mandrel. The subsequent cold-working causes the pipe to assume an inner surface contour matching on an incremental basis the outer surface of the mandrel.

The requirement of forcing the mandrel into the pipe, in combination with subsequent cold-working forming of the pipe on the mandrel, actually increases considerably the mechanical strength of the mold made out of the pipe particularly if the mandrel has fine surface finish. In addition to its fine finish, the mandrel should be very hard, so that forcing the pipe upon it and subsequent cold working of the pipe does not change the dimensions of the mandrel.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which:

FIG. 1, a through f, illustrates the steps of making a curved pipe mold in accordance with the preferred embodiment of the invention, showing the pipe in cross section; and

FIG. 2 is a cross section through the final product made in accordance with the method outlined in FIG. 1.

Proceeding now to the detailed description of the drawing in FIG. 1 thereof, there is illustrated at (a) a straight copper pipe 1 having Brinell hardness of approximately 30 to 35 kilograms (weight) per square millimeter (about 21 to 25 tons per square inches). The pipe or tubing from which pipe 1 has been cut may have been cold-drawn. The particular pipe section illustrated has been cut, for example, to a length at least approximately equal to the desired length of the mold to be made with a trifle added in length in order to take care of possible shortening during subsequent processing.

A mandrel 2 is provided, being hard and chromium-plated and having outer dimensions in accordance with the mold to be made. In particular, the mandrel 2 is curved, the curvature corresponding to the desired curvature the mold is to have for a particular continuous casting machine. The mandrel has constant cross section along its (curved) center axis.

Mandrel 2 is now introduced into pipe 1 and for its total length; this forces pipe 1 to assume in its interior the overall contour, particularly the curved contour of mandrel 2 and the result is as shown at (b) in FIG. 1. The interior surface of pipe 1 does not, however, have the exact surface contour of mam drel 2 on a surface increment by surface increment basis. Surface shaping is now obtained in the next step during which the pipe is subjectedto cold working and forming.

The mandrel with copper pipe thereon is forced through a thrust collar or ring 3 as illustrated at FIG. 1c. As a consequence, pipe 1 is forced in intimate surface-to-surface contact of the entire interior surface of pipe 1 on an incremental basis as the arrangement 1-2 passes through ring 3. As pipe I on mandrel 2 is forced through thrust ring 3, the copper pipe is cold-worked and the inner dimensions of the mold pipe assume surface detail of the mandrel within the required tolerances. Additionally, this process increases the Brinell hardness to more than twice its initial value, for example, up to 70 to kilograms (weighO-per square millimeter.

FIG. 1d illustrates the pipe-mandrel arrangement after having past through ring 3, and now mandrel 2 has to be removed from the pipe, whereby it has to be considered that now pipe 1 has considerable hardness, and is in tight surface engagement with the mandrel. However, the mandrel is to have fine surface finish at great hardnessand there is noresilient reaction between it and the cold-worked pipe. A stop plate with a central aperture, as illustrated at (e)-is now positioned against the front end of pipe 1, and mandrel -2 can be forced out of pipe 1 whereby in particular the rather hard pipe 1 rests against stopper plate 4 without changing dimensions during removal of the mandrel. After the mandrel has passed through and out of the pipe, the method is completed as shown at If.

FIG. 2 now illustrates the final product, ready for use as a mold in a continuous casting machine.

The invention has been illustrated in relation to a mold in which the interior cross section remains constant. This permitted the mandrel, in effect, to pass through pipe (FIG. la through I) in the same direction. The situation is quite analogous if a conical interior is desired, requiring a conical mandrel accordingly. Subsequent to cold working it will be necessary to force the mandrel out of the pipe in a direction opposite to insertion, i.e., in a direction colinear with the direction of increasing inner diameter of the mandrel.

It will also be apparent from the foregoing, that molds of still further configuration can be made with the method in accordance with the present invention. For example, a mandrel with rectangular, square-shaped, polygonal, etc., cross section may first be forced into a regular cylindrical pipe. Again, the interior of the pipe will assume overall configuration of the outer contour of that mandrel, without, however, intimate surface contact everywhere. Now cold working of the pipe forces the pipe into intimate contact with the mandrel for surface conformity everywhere. Generally, the initial step of forcing a suitably shaped mandrel into a pipe forces the latter to change its inner dimensions at least to the extent necessary to fully receive the mandrel and in surface contact therewith at least in isolated spots. The subsequent cold working and forming brings the remaining internal surface area of the pipe everywhere in intimate contact with the mandrel. The initial shaping of the pipe may be minute if the mold to be made is straight with cylindrical cross section using a pipe having already such contour, in which case the mandrel may merely reduce tolerances of the pipe. The initial shaping prior to cold working may be severe if there is a change in cross-sectional contour as well as from straight to curved extension along the center axis. in either case, however, subsequent cold working reduces contour and dimensional deviations between pipe and mandrel which increases the strength of the pipe.

The invention is not limited to the embodiments described above but all changes and modifications thereof not constituting departures from the spirit and scope of the invention are intended to be included.

We claim:

1. The method of making curved molds to be used for continuous casting, the combination comprising:

providing a straight, metallic pipe;

providing a curved mandrel having smooth outer surface with dimension and contour equivalent to the interior dimension of the mold to be made;

forcing the mandrel into the pipe for bending the pipe in accordance with the curving of the mandrel;

cold working and forming the pipe on the mandrel for the pipe to assume inner surface intimately matching the smooth outer contour of the mandrel thereby also strengthening the pipe; and

removing the mandrel from the hardened pipe.

2. The method as in claim 2, the outer dimensions of the mandrel being only slightly smaller than the inner dimensions of the pipe prior to the insertion of the mandrel into the pipe.

3. The method as in claim 1, the cold forming being conducted by moving the pipe with mandrel through a thrust ring thereby forcing the pipe into closely conforming surface contact with the mandrel.

4. The method as in claim 1, including the step of providing a mandrel of fine surface finish and considerable hardness.

5. The method as in claim 1, including the step of support-.

ing axially the pipe subsequent to the cold forming and forcing the mandrel out of the pipe in axial direction relative to the supported and stationary pipe. 

1. The method of making curved molds to be used for continuous casting, the combination comprising: providing a straight, metallic pipe; providing a curved mandrel having smooth outer surface with dimension and contour equivalent to the interior dimension of the mold to be made; forcing the mandrel into the pipe for bending the pipe in accordance with the curving of the mandrel; cold working and forming the pipe on the mandrel for the pipe to assume inner surface intimately matching the smooth outer contour of the mandrel thereby also strengthening the pipe; and removing the mandrel from the hardened pipe.
 2. The method as in claim 2, the outer dimensions of the mandrel being only slightly smaller than the inner dimensions of the pipe prior to the insertion of the mandrel into the pipe.
 3. The method as in claim 1, the cold forming being conducted by moving the pipe with mandrel through a thrust ring thereby forcing the pipe into closely conforming surface contact with the mandrel.
 4. The method as in claim 1, including the step of providing a mandrel of fine surface finish and considerable hardness.
 5. The method as in claim 1, including the step of supporting axially the pipe subsequent to the cold forming and forcing the mandrel out of the pipe in axial direction relative to the supported and stationary pipe. 